J Pathol Transl Med.  2023 Sep;57(5):278-283. 10.4132/jptm.2023.07.13.

Diagnostic conundrums of schwannomas: two cases highlighting morphological extremes and diagnostic challenges in biopsy specimens of soft tissue tumors

• Kim C
• Chung YG
• Jung CK

• KMID: 2545971
• DOI: http://doi.org/10.4132/jptm.2023.07.13

Abstract

Schwannomas are benign, slow-growing peripheral nerve sheath tumors commonly occurring in the head, neck, and flexor regions of the extremities. Although most schwannomas are easily diagnosable, their variable morphology can occasionally create difficulty in diagnosis. Reporting pathologists should be aware that schwannomas can exhibit a broad spectrum of morphological patterns. Clinical and radiological examinations can show correlation and should be performed, in conjunction with ancillary tests, when appropriate. Furthermore, deferring a definitive diagnosis until excision may be necessary for small biopsy specimens and frozen sections. This report underscores these challenges through examination of two unique schwannoma cases, one predominantly cellular and the other myxoid, both of which posed significant challenges in histological interpretation.

Keyword

Neurilemmoma; Soft tissue neoplasms; Biopsy; Frozen sections; Immunohistochemistry; Pathologists; Extremities; Mitosis

Figure

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  Fig. 1. A cellular schwannoma. (A) Magnetic resonance imaging scan showing a heterogeneously enhancing mass within the subcutaneous tissue plane. (B) Core biopsies showing predominantly cellular areas, resulting in a “blue appearance” accompanied by pale degenerate areas. (C) Compact spindle cells showing hypercellularity and mild nuclear pleomorphism. (D) S-100 immunohistochemistry showing a focal weak staining pattern despite high cellularity.

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  Fig. 2. Excision specimen of a cellular schwannoma. (A) Solid yellow-to-tan lesion with a surrounding thin fibrous capsule. (B) Hypercellular region without well-formed Verocay bodies. (C) One of the rare mitotic figures detected (white arrow). (D) Ki-67 labelling index less than 5%.

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  Fig. 3. A schwannoma with myxoid change. (A) Magnetic resonance imaging showing a T2-bright mass displaying heterogeneous enhancement. (B, C) Low- and high-power views of the frozen section showing scattered cytologically benign spindle cells with surrounding loose myxoid stroma.

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  Fig. 4. Excision specimen of a schwannoma with myxoid change. (A) Well-circumscribed, demonstrating a solid central area with a myxoid peripheral zone. (B) Interface between the loose myxoid area and more classic schwannoma-like area. Note that the classic area is observed at the deeper aspect. (C) High-power view exhibiting scattered spindle cells within the myxoid stroma.

Reference

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